There are increasing social and economic pressures to develop renewable energy sources as well as renewable and biodegradable industrial and consumer products and materials. The catalytic conversion of natural feedstocks to value-added products has resulted in new approaches and technologies whose application spans across the traditional economic sectors. There is a new focus on biorefining, which can be described as the processing of agricultural and forestry feedstocks capturing increased value by processing them into multiple products including platform chemicals, fuels, and consumer products. The conversion of tallow and other organic oils to biodiesel has been previously studied in depth. Traditionally, this conversion involves the trans-esterification of the triglyceride to produce three methyl-esterified fatty acids and a free glycerol molecule. The chemical, rheological, and combustion properties of the resulting “biodiesel” have also been extensively investigated. Unfortunately, these methyl-ester based fuels have been shown to be far more susceptible to oxidation and have lower heating values than the traditional petroleum based diesel fuels. As a result the traditional biodiesels must be blended with existing diesel stock and may also have to be supplemented with antioxidants to prolong storage life and avoid deposit formation in tanks, fuel systems, and filters.
If methyl-esterification can be considered a clean controlled reaction, a relatively crude alternative that has been utilized previously in industry is pyrolysis. Pyrolysis involves the use of a thermal treatment of an agricultural substrate to produce a liquid fuel product. Most literature reports utilize raw unprocessed agricultural commodities to produce a value-added fuel. Many different approaches to pyrolysis as a mechanism of producing a liquid fuel have been reported in the literature and fall under various regimes including flash, fast, and slow pyrolysis. The pyrolysis of a variety of agricultural products under these different regimes has been previously investigated, including castor oil, pine wood, sweet sorghum, and canola. Depending on the conditions used including the temperature used, residence time, and purity of substrate the balance of products produced varies between vapors, liquids, and residual solids (char).
One of the few studies to look at the pyrolysis of fatty acids instead of the triglycerides or more complex substrates focused on the pyrolysis of the salt of the fatty acid. The conditions used in the study were such that a homogeneous decarboxylation product was not produced. Instead a mixture of hydrocarbon breakdown products was produced and was not identified by the authors. In general, the decarboxylation of carboxylic acids that do not contain other interacting functional groups at high temperature and pressure is poorly understood in the literature. Gaining a better fundamental understanding of the chemistry and methodologies necessary to promote decarboxylation of fatty acids, or cracking reactions to larger smaller alkanes and alkenes, may allow the future development of new fuel and solvent technologies. In one aspect, described herein is the thermal treatment of fatty acids under anoxic conditions. Processes of this nature hold the potential to produce a higher grade fuel than the traditional biodiesels, and yet would potentially produce higher yields of desirable products than pyrolysis.